Classification of Legal Materials

published or submitted for publicatio

Heavy metal distribution for aqueous and solid phases in urban runoff, snowmelt and soils

At the start of the third millennium, over 50% of the world’s population lives in urban areas. Anthropogenic activities associated with urban development such as traffic generate significant particulate and heavy metal mass loadings. Ten urban highway sites located throughout the metropolitan area of Cincinnati, Ohio were studied. Storm water, snow and transportation land use soil/residual complexes (RSCs) were collected at each site. For the storm water, results are presented for a series of eight rainfall runoff events over a two-year period and included analyses between dissolved and particulate-bound fractions of heavy metals (Pb, Cu, Cd and Zn), and water quality characteristics such as hydrology, alkalinity, hardness and pH. For all sites, results are presented for a 460-mm snowfall in 1998 and included analyses between dissolved and particulate-bound fractions of heavy metals, particle size distributions (PSD), specific surface area (SSA), total surface area (SA), particle density (ρs), and water quality characteristics such as hardness, pH, conductivity, chloride, chemical oxygen demand (COD), and total suspended (TSS) and dissolved (TDS) solids. The role of climate and traffic were examined with respect to these results. For the RSCs, results included PSD, SSA, SA, ρs, particulate-bound fractions of heavy metals, mineralogical constituents and potentiometric titrations. Overall, partitioning analysis for storm water runoff indicated that heavy metals were predominately dissolved due to low pH, low alkalinity and short pavement residence times (τsf). Snow however had a much greater capacity to accumulate and retain particulate-bound metals due to a neutral pH, increased hardness and longer τsf in terms of days instead of minutes. The RSCs which retain and export storm water and snow had decreased levels of heavy metals when compared to the reference site. Although similar in parent material, the RSCs had different mineralogical constituents than the reference and exhibited a greater buffering capacity and net surface charge density. Heavy metal concentration at the undisturbed reference site indicated the potential of high atmospheric deposition from historical coal combustion. Characterization of partitioning, accretion and distribution of heavy metals is necessary for development of best management practices as source control in urban transportation land use areas

Soil and Slope Stability Study of Geomorphic Landform Profiles versus Approximate Original Contour for Valley Fill Designs

This report presents the findings of geotechnical testing on two material types retrieved from a surface mine site in Logan County, West Virginia, and investigates geomorphic landform design as an alternative in lieu of typical valley fill design and approximate original contour (AOC) surface mine reclamation design. Laboratory testing was carried out according to ASTM standard test methods. The scope of the testing performed involved grain size distribution analysis, hydrometer analysis, saturated shear strength testing under an insitu consolidation load, Atterberg limits including plastic and liquid limits, compaction at three predetermined compaction energies, and rigid wall permeameter hydraulic conductivity testing. Data was evaluated and analyzed to find to what degree the material particles moved under certain hydraulic gradients and if the particle movement affected the shear strength of the samples. The objectives of the testing were to understand the movement and behavior of small diameter soil particles at a valley fill and use the strength values as input parameters into several modules of GeoStudio(TM) for numerical slope stability modeling.;The numerical modeling involved geomorphic design for a proposed valley fill in southern West Virginia using commercial software following the Geofluv RTM method. A comprehensive seepage and slope stability analysis was then developed using the SEEP/W, SIGMA/W, and SLOPE/W modules of GeoStudio2007(TM) for assessing the groundwater flow characteristics of the blasted, unweathered sandstone fill, an insitu load calculation, and the resultant limit equilibrium analysis of slope stability (static factor of safety). These analyses were performed for both the AOC and geomorphic fill designs.;The cumulative analysis for the geomorphic valley fill alternative design yielded the highest factors of safety. Most cases produced factors of safety over 2.0. The failure locations were sought out to produce the lowest factors of safety for the structure. None of the factors of safety modeled yielded factors of safety under 1.0 for the geomorphic design. The results imply that the geomorphic design can remain very stable when a range of hydrologic conditions and geometries are applied.;Regulations require that reclaimed slope factors of safety must remain above 1.5. The analyses performed showed that the AOC valley fill design could withstand insitu loads and produced slope angles under most hydrologic conditions analyzed. Elevated pore pressures tended to result at the toe of the slope, and decreased the factor of safety. The most critical scenario was a fully saturated toe which yielded a factor of safety of 0.50.;If particle transport can occur and alter toe pore pressures, it is possible that some small slope failure may occur. The gradations that were found for the unweathered well graded sand with silt fill material showed that particle transport would not be a significant concern. The gradations that were found for the range of cases analyzed for the unweathered well graded sand with silt showed aggregation phenomena which could have implications on the long term stability of the earthen structures

Enhancement of superconductivity in NbN nanowires by negative electron-beam lithography with positive resist

We performed comparative experimental investigation of superconducting NbN nanowires which were prepared by means of positive-and negative electron-beam lithography with the same positive tone Poly-methyl-methacrylate (PMMA) resist. We show that nanowires with a thickness 4.9 nm and widths less than 100 nm demonstrate at 4.2 K higher critical temperature and higher density of critical and retrapping currents when they are prepared by negative lithography. Also the ratio of the experimental critical-current to the depairing critical current is larger for nanowires prepared by negative lithography. We associate the observed enhancement of superconducting properties with the difference in the degree of damage that nanowire edges sustain in the lithographic process. A whole range of advantages which is offered by the negative lithography with positive PMMA resist ensures high potential of this technology for improving performance metrics of superconducting nanowire singe-photon detectors

Unbound pavement base courses: Parallel study of stiffness and drainage characteristics

The purpose of this project was to study the effects of fines (minus #4 sieve) on permeability and stiffness characteristics of unbound base materials and to propose an optimumgradation that will satisfy these two parameters. One type of highway base material--crushed limestone--was used in the study. A total of 75 laboratory tests were conducted and distributed--25 respectively on permeability, resilient modulus and unconfined compression. The permeability test data were collected using a low-head permeameter. The resilient modulus and unconfined compression test data were collected by the mean of the MTS (Machine Testing System) with a load cell capacity of 22-kips. The major steps of the research are summarized as follows: (A) Conduct intensive laboratory testing on open and dense-graded materials with respect to their drainage (permeability) and stiffness (resilient modulus and unconfined compressive strength) characteristics. The determination of permeability is necessary if an evaluation of drainage capability of an existing or new base layer is needed. The determination of the resilient modulus is necessary because it is an input data for pavement design using the AASHTO procedure. (B) Perform permeability and resilient modulus tests to study the effect of introducing fines (percent passing #4) to open-graded base layers on permeability and resilient modulus. (C) From the data collected from these tests on both drainage and strength characteristics, perform regression analysis to develop formulas that relate percent fines to permeability and to resilient modulus. (D) Combine the tests results from permeability and resilient modulus to provide a range of percent fines gradation band that will satisfy the two parameters as pavement design inputs. (E) Provide some tools and techniques used to prevent the base course from being contaminated by subgrade material and to check whether the proposed base course is able to drain water as quickly as possible. The project produced some formulas that predict the coefficient of permeability for pavement base materials, unconfined compression strength, and resilient modulus. The study also provided an optimum gradation, permeable enough to withstand heavy traffic. A highway engineer can use these equations to estimate the coefficients of permeability and resilient modulus of aggregate bases for preliminary design or for evaluation of an existing unbound pavement layer

Static and cyclic response of ecoroof soil

Green technology in the United States has been on the rise over the past few decades in the United States. However, certain green technologies have been developed in the absence of design standards. Ecoroofs, which are vegetated soil masses placed on the top of a building’s roof structure, present several engineering concerns. Several important engineering concerns include overstressing of the roof structure due to ponding or excessive saturated soil dead loads during storm events, sliding of the ecoroof material causing overtopping or complete failure of the parapet walls during a seismic event, and the increase of inertial load at the top of the building. Standardization of ecoroof soil and the development of design codes for ecoroof systems in the United States would minimize the possibility of structural failure. Accordingly, this study presents the quantification of the geotechnical index properties and their variability, static stress-strain and volumetric response, and dynamic soil response and properties for ecoroof soil. A field exploration program, which included gathering undisturbed Shelby tube samples of ecoroof soil, was conducted in Portland, Oregon. The field exploration provided the basis for the geotechnical characterization of ecoroof soil. Sample statistics of the geotechnical index properties showed significant variability. Sieve testing showed that field samples of ecoroof soils tended to cluster; therefore, three target gradations were selected to serve as representative ecoroof gradations, which varied in the amount of fines present (i.e. material passing No. 200 sieve), median grain sizes, and uniformity of the gradation. Drained static simple shear tests were conducted on specimens reconstituted from each of the target gradations. The tests were performed to investigate the effect of relative density, applied vertical stress, and gradation on static shear strength, each of which contribute to variations in ecoroof strength. To understand the effect of organic matter on the strength parameters, three undisturbed specimens were sheared and the test results indicated that the organic content has significant influence on the volumetric and stress-strain response of ecoroof soil. Preliminary dynamic soil properties, such as the modulus reduction and damping characteristics, and the liquefaction susceptibility of ecoroof soil was determined from a series of undrained cyclic simple shear tests on reconstituted and undisturbed tube specimens. Many reconstituted ecoroof soil specimens exhibited liquefaction under undrained cyclic strain controlled conditions, and variations in liquefaction susceptibility, were attributed to the type of soil gradation. Cyclic simple shear tests on undisturbed tube specimen specimens indicated that the organic content influences the dynamic response of ecoroof soil. Accordingly, this study provides a baseline with which practicing engineers can begin to assess the loading associated with ecoroof soil, and may be used to guide future studies and code development